They're 50-80k a tire on a cat797 and the truck has 6. Mine roads aren't the same as normal people roads, top layer can vary between what you see on a gravel road to basically really crap with chunks bigger than your fist. Add on to that you're carrying anywhere between 60 to 400 tons.
Most work vehicles rarely go above 10 mph, and could probably get away with non-air-filled tyres made of steel if necessary. They'd last forever then.